Leader for fly fishing

ABSTRACT

A leader for fly fishing which has a high knot strength and a high tensile tenacity, is free from the formation of a shape-unstable portion (constriction) having a smaller diameter than an average thread diameter of the tippet section and the occurrence of melt fracture at a connecting portion between the tapered section and the tippet section, and shows an excellent natural drift property, can be produced by using a vinylidene fluoride-based resin having an inherent viscosity of 1.0 to 1.7 dl/g.

TECHNICAL FIELD

The present invention relates to a leader for fly fishing. Moreparticularly, the present invention relates to a leader for fly fishing,which comprises a butt section, a tapered section and a tippet section;comprises a vinylidene fluoride-based resin whose viscosity lies in aspecific range, thereby exhibiting a high tensile strength or tenacity;and is so improved as to inhibit a shape-unstable portion (constriction)having a smaller diameter than an average diameter of the tippetsection, and melt fracture from being formed at a connecting portionbetween the tapered section and the tippet section, thereby exhibitingan excellent natural drift property.

BACKGROUND ART

The fly fishing is a fishing method of casting a fly without weight andfloat from a remote position unable to be sensed by fishes, and driftingthe fly on or in water. To meet such requirements, in the fly fishing,there has been used a five-part fishing equipment comprising a fly rod,a reel, a fly line, a leader and a fly.

Among these parts, as the leader, there have been preferably used thoseleaders which are reduced in thread diameter to realize natural driftthereof. The leader has been further required to have a tapered sectionthrough which an inertia force is smoothly transmitted from the fly lineto the fly upon casting, thereby enabling the fly to be quietly droppedon a water surface. Consequently, the leader has been usually composedof a portion called “butt” and having a larger thread diameter, which isconnected with the fly line, a portion called “taper” and having atapered shape, and a portion called “tippet” and having a smaller threaddiameter, at which the fly is fitted to the leader. Incidentally, inFIG. 1(a) showing an explanatory view of the above-mentioned leader,reference numeral (1) represents the leader, (2) represents the buttsection (A), (3) represents the tapered section (B), and (4) representsthe tippet section (C).

In addition, the leader is preferably comprising a material whoserefractive index is close to that of water, so as to be unsensed byfishes. As such the materials having a refractive index close to that ofwater, there may be exemplified vinylidene fluoride-based resins.However, when the vinylidene fluoride-based resins are subjected tospinning process, it has been difficult to obtain a leader having asmooth shape. Especially, in the production of a tapered leader, ashape-unstable portion 6 (constriction) having a smaller diameter thanan average diameter of the tipped section is formed at a connectingportion between the tapered section (B) and the tippet section (C), sothat a stress due to tension caused upon fishing-up is concentrated onthe constricted portion, thereby causing the leader to be cut thereat.

Further, in the case where the vinylidene fluoride-based resins aresubjected to the spinning process, the obtained leader tends to sufferfrom melt fracture. Especially, the melt fracture is more remarkablycaused upon the production of tapered leaders. That is, since thetapered leader is composed of the butt section (A), the tapered section(B) and the tippet section (C), it is required that the diameter of theleader is varied corresponding to the respective sections, so that themelt fracture is likely to occur. When a raw thread having such meltfracture is stretched to impart a mechanical strength thereto, the rawthread not only suffers from breakage but also is deteriorated inappearance of the surface thereof. Further, when vinylidenefluoride-based resins having an inherent viscosity less than thespecific value is used to produce a leader, the obtained leader isdeteriorated in natural drift property.

The present invention has been attained to overcome the above-mentionedproblems. It is an object of the present invention to provide a leaderfor fly fishing which comprises a vinylidene fluoride-based resin, canshow a high tensile strength or tenacity, is improved so as to inhibit ashape-unstable portion 6 (constriction) having a smaller diameter thanan average diameter of the tippet section and melt fracture from beingformed at a connecting portion between the tapered section (B) and thetippet section (C), and can exhibit an excellent natural drift propertyand a good appearance.

DISCLOSURE OF THE INVENTION

That is, in an aspect of the present invention, there is provided aleader for fly fishing, which comprises a vinylidene fluoride-basedresin, and comprises a butt section, a tapered section and a tippetsection, the inherent viscosity of the vinylidene fluoride-based resinbeing 1.0 to 1.7 dl/g.

The present invention is explained in detail below. The leader for flyfishing according to the present invention (hereinafter referred tomerely as “leader”) is formed of a vinylidene fluoride resin-basedmonofilament, and is a so-called knotless tapered leader. As thevinylidene fluoride-based resin as a raw material, there may beexemplified vinylidene fluoride-based homopolymers, vinylidenefluoride-based copolymers or a mixture thereof.

It is necessary that the vinylidene fluoride-based copolymers areselected from those capable of exhibiting a ductility and a strengthwhich are acceptable for the knotless tapered leader. As the vinylidenefluoride-based copolymers capable of satisfying these requirements,there may be exemplified copolymers of vinylidene fluoride and ethylenetetrafluoride, propylene hexafluoride, ethylene trifluoride, ethylenechloride trifluoride, vinyl fluoride or the like. These monomers otherthan vinylidene fluoride can be used singly or in combination of two ormore thereof.

The inherent viscosity of the vinylidene fluoride-based resin as a rawresin of the leader, is 1.0 to 1.7 dl/g, preferably 1.10 to 1.35 dl/g,more preferably 1.15 to 1.35 dl/g, still more preferably 1.20 to 1.35dl/g. When the inherent viscosity is less than 1.0 dl/g, the obtainedleader cannot have a high tensile tenacity and it becomes difficult tocontrol a length of the leader upon the production thereof, resulting intoo long tapered section. The leader for fly fishing has been usuallysold and used by a predetermined length, so that when the taperedsection is elongated, the lengths of the remaining butt and tippetsections can no longer be increased. It is disadvantageous that such aleader cannot maintain a good natural drift property, thereby failing toaccurately attack an aimed fishing point.

Meanwhile, in order to reduce the length of the tapered section, it maybe considered to be reasonable that the time required for varying anextrusion output of the vinylidene fluoride-based resin and a take-offspeed of the obtained thread is shortened. However, the varying time isusually about one second. When the varying time is shortened to lessthan one second, it takes a long time to stabilize the extrusion outputand the take-off speed, so that unevenness of thread tends be formed atthe butt and tippet sections.

When the inherent viscosity exceeds 1.7 dl/g, there may be a tendencythat an shape-unstable portion 6 (constriction) having a smallerdiameter than an average diameter of the tippet section is generated ata connecting portion between the tapered section (B) and the tippetsection (C), so that a stress is concentrated on the constricted portionupon fishing-up, thereby causing thread breakage of the leader. Besides,the melt fracture tends to be caused at the connecting portion, so thatwhen the leader is stretched, thread breakage is likely to occur and thesurface of the obtained leader is deteriorated in appearance.

The vinylidene fluoride-based resins may further contain a plasticizer,a heat stabilizer, an acrylic resin, a crystal nucleating agent, alubricant or the like. Especially, in order to smoothly cast the leaderor accurately drop the fly on the aimed fishing position, it is requiredthat curl or kink of the leader reeled can be readily eliminated whenunreeled. For this reason, it is preferred to add the plasticizer in anamount of 1 to 10% by weight.

As the plasticizers added to the vinylidene fluoride-based resins, theremay be exemplified aliphatic polyesters. Examples of the preferredaliphatic polyesters may include aliphatic polyesters produced fromesters of aliphatic dialcohol having 2 to 4 carbon atoms and aliphaticdicarboxylic acid having 2 to 6 carbon atoms, and aliphatic polyestersproduced from cyclic esters having 3- to 7-membered ring. As thealiphatic dialcohols having 2 to 4 carbon atoms, there may beexemplified ethylene glycol, propylene glycol, 1,4-butane diol,1,2-butane diol or the like. As the aliphatic dicarboxylic acids having2 to 6 carbon atoms, there may be exemplified oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid or the like.

In addition, as the cyclic esters having 3- to 7-membered ring, theremay be exemplified β-propiolactone, γ-butylolactone, δ-valerolactone,ε-caprolactone or the like.

It is preferred to use a composition obtained by mixing the vinylidenefluoride-based resin with the plasticizer using a ribbon blender, ahigh-speed mixer (Henschel mixer), a fixed V-type blender, a tumbler, aball mill or the like, further mixing the resultant mixture withadditives, if required, using a blender, and then melt-kneading theobtained mixture using an extruder.

As the melt-spinning temperature, there may be adopted any temperaturein the range of not less than a melting point of the vinylidenefluoride-based resin used and not more than a thermal decompositiontemperature thereof. In order to maintain a stable spinning property,the melt-spinning temperature is usually 200 to 300° C., preferably 230to 280° C.

The amount of the vinylidene fluoride-based resin discharged andmelt-extruded from a spinning nozzle of the extruder and the take-offspeed of the raw thread may be controlled according as respective threaddiameters and lengths of the butt section, the tapered section and thetippet section.

For example, in the case where the butt section having a raw threaddiameter of 800 to 1,800 μm, the tapered section and the tippet sectionhaving a thread diameter of 280 to 1,100 mm are successively formed, theamount of resin discharged for the butt section is 1.0 to 3.5 cc/min andthe take-off speed thereof is 1 to 3 m/min; and the amount of resindischarged for the tippet section is 0.5 to 3.0 cc/min and the take-offspeed thereof is 3 to 10 m/min. Further, by varying a rotating speed ofa gear pump and a peripheral speed of pinch rolls, the amount of resindischarged for the butt section is reduced to 10 to 90% and the take-offspeed thereof is increased to 100 to 1,000%, for 0.5 to 3 seconds,thereby forming the tapered section.

In the course of varying the above-mentioned amount discharged and thetake-off speed (for 0.5 to 3 seconds), the tapered section and then thetippet section are formed. Also, when the tippet section, the taperedsection and the butt section are formed in this order, theabove-mentioned step of varying the amount discharged and the take-offspeed may be conversely conducted.

In the production of the raw thread, the distance (air gap) between thespinning nozzle and a cooling bath may be set to usually 20 to 300 mm,preferably 30 to 250 mm.

After passing through the air gap, the molten vinylidene fluoride-basedresin is cooled in the cooling bath and then solidified. As the coolantsused in the cooling bath, there may be exemplified water, inorganicsalt-containing water, alcohols, polyethylene glycol, glycerol andmixtures thereof. The cooling temperature is preferably less than such atemperature that bubbles due to boiling are formed at an interfacebetween the coolant and the molten resin. For example, when the coolantis water, the cooling temperature may be usually 20 to 50° C.,preferably 30 to 45° C.

The above-mentioned tapered raw thread comprising the vinylidenefluoride-based resin is stretched in a bath at a temperature of 150 to300° C. As the heating medium used in the stretching bath, there may beexemplified liquid heating media such as boiling water or glycerol,gaseous heating media such as air, steam or a nitrogen gas, or the like.Among these heating media, glycerol is preferred. In the case where theliquid heating medium is used, the stretching temperature is preferably150 to 180° C. Especially when the glycerol is used, the stretchingtemperature is more preferably 160 to 175° C., still more preferably 165to 172° C. In the case where the gaseous heating medium is used, thestretching temperature is preferably 200 to 250° C.

The stretching of the tapered raw thread may be conducted either at asingle stage or at two or more multiple stages. From the standpoint ofimprovement in strength, the total stretching ratio is usually 4.0 to7.0 times, preferably 4.5 to 6.5 times, more preferably 4.8 to 6.3times.

After stretching, the tapered raw thread may be subjected to relaxationheat-treatment. The temperature used in the relaxation heat-treatment isusually 70 to 180° C., and the percentage of relaxation is usually 2 to10%. Further, in the case where the leader is floated over a watersurface upon use, the leader obtained by the above-mentioned method maybe coated with a water repellant or an oiling agent.

The thread diameters of the respective sections of the leader areusually as follows. The thread diameter of the butt section is usually300 to 800 μm; and the thread diameter of the tippet section is usually50 to 600 μm. In general, there have been used such leaders having aratio value of a thread diameter of the tippet section to that of thebutt section of 0.1 to 0.7.

The leader comprising a vinylidene fluoride-based resin according to thepresent invention has an inherent viscosity of 1.0 to 1.7 dl/g. As aresult, there can be provided a leader which can exhibit a high tensiletenacity, is free from the formation of a shape-unstable portion(constriction) having a smaller diameter than an average thread diameterof the tippet section and the occurrence o melt fracture at a connectingportion between the tapered section and the tippet section, and can showan excellent natural drift property and a good appearance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is an explanatory view of a leader; and

FIG. 1(b) is an enlarged view of a connecting portion (5) of the leader(1) shown in FIG. 1(a).

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described in more detail withreference to the following examples, but the present invention is notrestricted to the examples and various other modification are possiblewithout deviating from the scope of the invention. The evaluationmethods are as follows.

(1) Thread diameter: The change in thread diameter was measured at athread transporting speed of 2 m/min by using an outerdiameter-measuring device (a laser outer diameter-measuring device“L-3100” manufactured by KEYENCE CO., LTD.).

From the results of the above thread diameter measurements, an averagevalue of the maximum and minimum thread diameters of the tippet sectionwas determined as an average thread diameter of the tippet section, andan average value of the maximum and minimum thread diameters of the buttsection was determined as an average thread diameter of the buttsection.

(2) Strength and tenacity test: Ten leader samples each having a lengthof 30 cm were measured at 23° C. and an elastic stress rate of 300mm/min by using a tensile tester (TENSILON “UT-M-III-100” manufacturedby ORIENTEC CO., LTD.), thereby determining a knot tenacity of thetippet section of each sample. The knot strength was obtained bydividing the measured knot tenacity by a sectional area of the averagethread diameter of the tippet section. Also, the tensile tenacity ofeach leader sample was measured under the same conditions as describedabove.

(3) Inherent viscosity: The inherent viscosity of a resin compositionprepared by using dimethyl acetamide as a solvent and having aconcentration of 0.4 g/dl was measured at 30° C.

(4) Existence or non-existence of constriction: The change in threaddiameter was measured by using the above-mentioned outerdiameter-measuring device to determine whether or not the constrictionwas caused.

(5) Occurrence or non-occurrence of melt fracture: The diameter of theraw thread was observed at a magnification of 40 times by using amicroscope to determine whether or not the melt fracture was caused.

(6) Natural drift property: Using a fishing rod equipped with a reelonto which a leader obtained in each Example, a fly line and a fly wereset, ten persons having a fly-fishing experience of not less than fiveyears have played fly-fishing to determine whether or not the fly wasable to continue a natural drift and whether or not the aimed fishingpoint was accurately attacked. The natural drift property was evaluatedby classifying the results into three ranks shown in the following Table1, and then an average thereof was obtained.

TABLE 1 ◯: Natural drift of the fly was able to be continued and theaimed fishing point was able to be accurately attacked. Δ: it was ratherdifficult to continue the natural drift and accurately attack the aimedfishing point. X: it was extremely difficult to continue the naturaldrift and accurately attack the aimed fishing point.

EXAMPLES 1 TO 4 AND COMPARATIVE EXAMPLES 1 TO 2

100 parts by weight of each of vinylidene fluoride-based resins eachhaving an inherent viscosity shown in Table 2 and 5 parts by weight of apolyester plasticizer (aliphatic polyester composed of two aliphaticdiols, i.e., propylene glycol and butane diol, and one aliphaticdicarboxylic acid, i.e., adipic acid) were mixed together by a Henschelmixer. The mixture was formed into pellets by using an extruder having adiameter of 35 mm.

The thus obtained pellets were extruded at 280° C. from six holes of anozzle each having a diameter of 1.3 mm such that the amount dischargedper one hole was A cc/mn shown in Table 2, and then passed through acooling bath maintained at a temperature of 43° C. The thus obtained rawthread (butt section) was taken off by pinch rolls rotated at a take-offspeed of A m/min for 15 seconds. Next, the amount discharged and thetake-off speed were changed to B cc/min and B m/min, respectively, forone second. Then these conditions were maintained for 30 seconds to takeoff the raw thread (tippet section). Further, the amount discharged andthe take-off speed were changed again to A cc/min and A m/min,respectively, for one second, and then such conditions were maintainedfor 15 seconds to take off the raw thread (butt portion). These stepswere periodically repeated, thereby obtaining a tapered raw thread.

The thus obtained tapered raw thread was stretched in a glycerol bathmaintained at a temperature of 169° C. at a stretching ratio of 5.6times. The stretched raw thread was further subjected to 3% relaxationtreatment in 80° C. warm water, and then cut into a leader composed ofbutt and tippet sections each having a length of 1 m. The spinningconditions and the properties of the obtained leader are shown in Table2.

In Table 2, in the case of Comparative Example 2, since the raw threadwas broken upon stretching, non-stretched raw thread was observed todetermine whether or not the constriction and melt fracture were caused.When the inherent viscosity was less than 1.0 dl/g, both the knotstrength and the tensile tenacity thereof were low and the length of thetapered section was large, so that it became extremely difficult tomaintain continuous natural drift property and accurately attack theaimed fishing point (Comparative Example 1). On the other hand, when theinherent viscosity was more than 1.7 dl/g, the raw thread suffered frombreakage upon stretching (Comparative Example 2).

TABLE 2 Comparative Examples Examples 1 2 3 4 5 1 2 Inherent viscosity1.00 1.15 1.20 1.35 1.70 0.80 1.90 (dl/g) Air gap (mm) 100 100 100 100100 100 100 Take-off speed A 1.8 1.8 1.8 1.8 1.8 1.8 1.8 (m/min) Amountdischarged A 1.3 1.3 1.3 1.3 1.3 1.3 1.3 (cc/min) Take-off speed B 5.05.0 5.0 5.0 5.0 5.0 5.0 (m/min) Amount discharged B 0.6 0.6 0.6 0.6 0.60.6 0.6 (cc/min) Average diameter of 410 410 410 410 410 410 410 buttsection (μm) Average diameter of 165 165 165 165 165 165 — tippetsection (μm) Length of tapered 1.0 1.0 0.9 0.9 0.9 1.4 — section (m)Knot strength of 60 63 63 62 60 38 — tippet section (kg/mm²) Tensiletenacity of 1.5 1.7 1.9 1.8 1.5 1.0 — leader (kg) Existence of None NoneNone None None None Yes constriction Occurrence of melt None None NoneNone None None Yes fracture Natural draft ◯ ◯ ◯ ◯ ◯ × — propert

INDUSTRIAL APPLICABILITY

As described above, in accordance with the present invention, there isprovided a useful leader comprising a vinylidene fluoride-based resinhaving an inherent viscosity of 1.0 to 1.7 dl/g which is free from theformation of a shape-unstable portion (constriction) having a smallerdiameter than an average thread diameter of the tippet section and theoccurrence of melt fracture at a connecting portion between the taperedsection and the tippet section, and can show an excellent natural driftproperty, a high knot strength and a high tensile tenacity.

What is claimed is:
 1. A leader for fly fishing comprising a vinylidenefluoride-based resin having an inherent viscosity of 1.0 to 1.7 dl/g,and comprising a butt section, a tapered section and a tippet section,the thread diameter of the butt section being 300 to 800 μm, the threaddiameter of the tippet section being 50 to 600 μm, and the ratio valueof the thread diameter of the tippet section to that of the butt sectionbeing 0.1 to 0.7.
 2. The leader for fly fishing according to claim 1,wherein the inherent viscosity is 1.10 to 1.35 dl/g.
 3. The leader forfly fishing according to claim 1 or claim 2, wherein the inherentviscosity is 1.15 to 1.35 dl/g.
 4. A leader for fly fishing according toclaim 1, which is produced by melt-spinning the vinylidenefluoride-based resin at a temperature of 200 to 300° C. to produce atapered raw thread, and stretching the obtained tapered raw thread in abath at a temperature of 150 to 300° C., wherein the amount of resindischarged forming the butt section is 1.0 to 3.5 cc/min and a take-offspeed thereof is 1 to 3 m/min, the amount of resin discharged formingthe butt section is reduced to 10 to 90% and the take-off speed thereofis increased to 100 to 1,000% for 0.5 to 3 seconds by varying a rotatingspeed of a gear pump and a peripheral speed of pinch rolls, and theamount of resin discharged forming the tippet section is 0.5 to 3.0cc/min and the take-off speed thereof is 3 to 10 m/min.